The present invention relates to an electrical power source.
There are many circumstances in which it is necessary to be able to power electrical equipment for which there is no ready access to a mains power supply. For example power supplies are required for communications equipment, electronic sensors and other devices, small motors and lights. Such devices typically require milliwatts or decawatts of power and in the past the only option in such circumstances has been the use of electrical batteries. Batteries require regular replacement which is a major disadvantage associated with their use.
Electronic sensors comprising ceramic electrolytes with electrodes made of platinum are known. Unfortunately, typically they produce only microwatts of power which is too small in many applications.
It is an object of the present invention to provide a fuel cell system suitable for replacing batteries as an electrical power source.
According to the present invention, there is provided an electrical power source comprising a fuel gas supply, means for delivering an air/fuel gas mixture to a catalytic oxidation device such that the catalytic oxidation device is heated by oxidation of fuel gas, a fuel cell located so as to be heated as a result of the heating of the catalytic oxidation device, and means for delivering air and fuel gas to the fuel cell, the fuel cell when heated and supplied with air and fuel generating an electrical output.
The power source may be supplied with fuel gas from a bottle or any other available source of fuel gas. The fuel gas supply may be connected to an injector arranged to draw ambient air into a conduit connected to the catalytic oxidation device, the air and fuel gas being mixed in the conduit. Preferably the catalytic oxidation device is connected in series with and upstream of the fuel cell in the conduit.
A further catalytic oxidation device may be provided downstream of the fuel cell to consume any residual fuel gas. The fuel cell may be defined by one or more ceramic tubes through which the fuel gas flows. Such tubes may be formed from zirconium oxide doped with yttria. The or each catalytic oxidation device may be formed from a porous mass of ceramic fibres supporting a platinum catalyst.
A sulphur absorbent filter may be provided upstream of the catalytic oxidation device, and the catalytic oxidation device and fuel cell may be located within a thermally insulating jacket.